High Speed Packet Access (HSPA) is an amalgamation of two mobile protocols—High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA)—that extends and improves the performance of existing 3G mobile telecommunication networks using the WCDMA protocols. A further-improved 3GPP standard called Evolved High Speed Packet Access (also known as HSPA+) was released late in 2008, with subsequent worldwide adoption beginning in 2010. The newer standard allows bit rates to reach as high as 337 Mbit/s in the downlink and 34 Mbit/s in the uplink; however, these speeds are rarely achieved in practice.
Overview The first HSPA specifications supported increased peak data rates of up to 14 Mbit/s in the downlink and 5.76 Mbit/s in the uplink. They also reduced latency and provided up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink compared with original WCDMA protocol.
High Speed Downlink Packet Access (HSDPA)
High Speed Downlink Packet Access (HSDPA) is an enhanced 3G (third-generation) mobile communications protocol in the High-Speed Packet Access (HSPA) family. HSDPA is also known as 3.5G and 3G+. It allows networks based on the Universal Mobile Telecommunications System (UMTS) to have higher data speeds and capacity. HSDPA also decreases latency, and therefore the round-trip time for applications. HSDPA was introduced in 3GPP Release 5. It was accompanied by an improvement to the uplink that provided a new bearer of 384 kbit/s (the previous maximum bearer was 128 kbit/s). Evolved High Speed Packet Access (HSPA+), introduced in 3GPP Release 7, further increased data rates by adding 64QAM modulation, MIMO, and Dual-Carrier HSDPA operation. Under 3GPP Release 11, even higher speeds of up to 337.5 Mbit/s were possible. The first phase of HSDPA was specified in 3GPP Release 5. This phase introduced new basic functions and was aimed to achieve peak data rates of 14.0 Mbit/s with significantly reduced latency. The improvement in speed and latency reduced the cost per bit and enhanced support for high-performance packet data applications. HSDPA is based on shared channel transmission, and its key features are shared channel and multi-code transmission, higher-order modulation, short Transmission Time Interval (TTI), fast link adaptation and scheduling, and fast hybrid automatic repeat request (HARQ). Additional new features include the High Speed Downlink Shared Channels (HS-DSCH), quadrature phase-shift keying, 16-quadrature amplitude modulation, and the High Speed Medium Access protocol (MAC-hs) in base stations. The upgrade to HSDPA is often just a software update for WCDMA networks. In HSDPA, voice calls are usually prioritized over data transfer.
User equipment categories The following table is derived from table 5.1a of the release 11 of 3GPP TS 25.306 and shows maximum data rates of different device classes and by what combination of features they are achieved. The per-cell, per-stream data rate is limited by the "maximum number of bits of an HS-DSCH transport block received within an HS-DSCH TTI" and the "minimum inter-TTI interval". The TTI is 2 milliseconds. So, for example, Cat 10 can decode 27,952 bits / 2 ms = 13.976 Mbit/s (and not 14.4 Mbit/s as often claimed incorrectly). Categories 1-4 and 11 have inter-TTI intervals of 2 or 3, which reduces the maximum data rate by that factor. Dual-Cell and MIMO 2x2 each multiply the maximum data rate by 2, because multiple independent transport blocks are transmitted over different carriers or spatial streams, respectively. The data rates given in the table are rounded to one decimal point.
Further UE categories were defined from 3GGP Release 7 onwards as Evolved HSPA (HSPA+) and are listed in Evolved HSDPA UE Categories.
Notes
Adoption
As of 28 August 2009, 250 HSDPA networks had commercially launched mobile broadband services in 109 countries. 169 HSDPA networks supported 3.6 Mbit/s peak downlink data throughput, and a growing number delivered 21 Mbit/s peak data downlink. CDMA2000-EVDO networks had the early lead on performance. In particular, Japanese providers were highly successful benchmarks for this network standard. However, this later changed in favor of HSDPA, as an increasing number of providers worldwide began adopting it. In 2007, an increasing number of telcos worldwide began selling HSDPA USB modems to provide mobile broadband connections. In addition, the popularity of HSDPA landline replacement boxes grew—these provided HSDPA for data via Ethernet and Wi-Fi, as well as ports for connecting traditional landline telephones. Some were marketed with connection speeds of "up to 7.2 Mbit/s" under ideal conditions. However, these services could be slower, such as when in fringe coverage indoors.
High Speed Uplink Packet Access (HSUPA) High-Speed Uplink Packet Access (HSUPA) is a 3G mobile telephony protocol in the HSPA family. It is specified and standardized in 3GPP Release 6 to improve the uplink data rate to 5.76 Mbit/s, extend capacity, and reduce latency. Together with additional improvements, this allows for new features such as Voice over Internet Protocol (VoIP), uploading pictures, and sending large e-mail messages. HSUPA was the second major step in the UMTS evolution process. It has since been superseded by newer technologies with higher transfer rates, such as LTE (150 Mbit/s for downlink and 50 Mbit/s for uplink) and LTE Advanced (maximum downlink rates of over 1 Gbit/s).
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